Iodine is a very important trace element necessary in the biosynthesis of thyroid hormones. Iodine is required for developing and maintaining a healthy body. There are well known Iodine Deficiency Disorders like Goiter and Cretinism.
Reference may be made to Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition (electronic version), 2002, wherein it is stated under Toxicology and Occupational Health of Iodine and its compounds that: “Iodine is absorbed by the body and concentrated in the form of diiodotyrosine and triiodothyronine, which form thyroxine that is stored as thyroglobulin. Thyroxine is secreted by the thyroid, enters the circulation, and is carried to the peripheral tissues where it controls tissue metabolism primarily through regulation of enzyme activities. Iodine is essential to higher animals and humans. A normal person requires about 75 mg of iodine per year.
Reference may be made to the same reference wherein under Biosynthesis of Thyroid Hormones it is stated that: “The healthy thyroid gland takes up approximately 75 μg of iodine per day, provided enough dietary iodine is available (150-300 μg/d). Iodine is used to iodinate the tyrosine residues of a thyroid-specific protein thyroglobulin. The resulting 3,5-diiodotyrosine groups in the peptide chain of thyroglobulin react with each other or 3-monoiodotyrosine to form thyroxine (3,5,3′,5′-tetraiodothyronine) or triiodothyronine, respectively. This thyroxine- and triiodothyroninecontaining thyroglobulin is stored in the colloid within the thyroid follicle. The normal human thyroid contains approximately 10 mg of iodine in this form. During secretion, thyroglobulin leaves the colloid and is hydrolyzed by the surrounding follicular cells. The liberated hormones, thyroxine (T4) and triiodothyronine (T3), are released into the blood at rates of ca. 100 and 8 μg/d, respectively.”
The edible salt is chosen as a vehicle in the provision of iodine because of its uniform consumption and availability to all segments of the population independent of social or economic status. During the past twenty years, there has been a strong effort, lead by the United Nations, to iodize all salt for human consumption. Reference may be made to Ullmann's Encyclopedia above wherein it is stated that the iodine required by the body “is usually consumed as iodized salt that contains one part sodium or potassium iodide to 100,000 parts of sodium chloride.” Reference may also be made to the book entitled “Endemic Goitre”, by F. W. Clements et al., published by WHO in 1960 wherein it is stated that The Food and Nutrition Board of National Research Council of the USA placed the optimum requirement of iodine at 150-300 μg per day, and considering 10 gm of salt consumption per day, the iodisation level of salt could be around 15-30 mg per kg of salt.
Reference may be to the paper by R. Aquaron in Proceedings of 8th World Salt Symposium, 2000, Vol. 2, pp 935-940 wherein the author has tabulated the information on the types of iodizing agent used in different countries. The table shows that either iodide or iodate is used singly for salt iodization. There is no mention of any other option of salt iodization.
Reference may be made to the article by J. T. Dunn in the book entitled “S.O.S for a billion” edited by B. S. Hetzel and C. S. Pandav, 1994, pp 108-109, wherein the use of iodized vegetable oils, and particularly a single injection of Lipiodol that contains 480 mg of iodine covalently bound to 1 ml of poppy seed oil, is reported to be useful for cure of severe iodine deficiency disorders. While this methodology is useful for correction of severe cases of iodine deficiency, it is not popular as a matter of routine.
Reference may be made to the same article (pp 113-114) above wherein it is stated that water could be used as a vehicle for introducing iodine. The water was iodinated using iodine crystals before supply to the community. It specifically states that: “Iodine at a level of 500 μg/l has been used in community water supplies to reduce bacterial pollution. This iodine is available to the thyroid, and will certainly correct any iodine deficiency present, without any apparent problems from excessive iodine intake.” The authors further go on to state that: “There has been continued interest in the possibility of using iodine to correct iodine deficiency and purify water at the same time. Many rural communities in developing countries share both the problems; so a joint solution would be attractive, and further investigation is needed. Only iodine in chemical form is effective, potassium iodide and potassium iodate are not.”
Reference may be made to httn://www.extention.umn.edu/, University of Minnesota Extension Service home page, on topic entitled “Iodine-rich Drinking Water (Tubig Talino)—A Boost to Iodine Deficiency Disorders Control Program”, wherein it is reported that iodine rich water is prepared, named as “water+I2” which can be mixed with potable water in prescribed proportion to supply daily intake of iodine in form of elemental iodine. While delivery of elemental iodine via the vehicle of water is reported above there is no corresponding prior art for salt.
Reference may be made to a paper entitled “Investigation on the stability of iodide and iodate in table salts in Iran and the determination of its impurities” by F. Halek and S. Boghozian, published in Proceedings of 8th World Salt Symposium, 2000, Vol. 2, pp 1251-1252, wherein they have reported that although iodide should be preferred over iodate for better bioavailability, the latter is used for salt iodization in view of its higher chemical stability, especially when climatic factors and salt purity are not conducive for use of iodide. No effort is made to stabilize iodide in such salt not to mention of any efforts towards use of both iodide and iodate together as a source of latent iodine.
Reference may be made to a book entitled “Pharmacology & Pharmaco-Therapeutic” by V. Iswariah and M. N. Guruswami, 1979, pp 548, wherein the following comment is made regarding iodine metabolism: “In addition to elemental iodine, iodides of potassium and sodium may be used to obtain systemic effects of iodine . . . Iodates are of no value.”
Reference may be made to a paper entitled “The stability of potassium iodate in crude table salt”, by Arroyave, G. et. al., in Bull. World Health Organisation, 1956, 14, pp 183-155, wherein potassium iodate was stabilized by calcium carbonate in crude sea salt stored in hemp fiber sacks for up to eight months at ambient temperatures and relative humidity between 70 and 84%. Only some 3.5% of added iodine was reported to be lost. The work only deals with stability of iodate in pure form.
Reference may be made to the Indian patent application No. 1219/DEL2004 dated 30 Jun. 2004 (also filed in U.S.A. and under PCT) by P. K. Ghosh et. al. wherein the authors have prepared a novel iodizing agent in which synthetic hydrotalcite type compound is used to intercalate iodate anion in the compound matrix. They have claimed to have completely suppressed the loss of iodine from iodised salt. The work deals with stability of iodate only in pure form.
Reference may be made to a paper entitled “Micro encapsulation for iodine stability in salt fortified with ferrous fumarate and potassium iodide” by Diosady L. L. et. al., in Food Research International, 2002, Volume 35, Issue 7, pp 635-642 wherein potassium iodide or potassium iodate was encapsulated in modified starches, gelatin, sodium hexametaphosphate and purified sodium chloride by spray drying and fluidized bed drying to produce microcapsules containing 0.3 to 2% iodine. The work is of relevance to preparation of double fortified salt but does not teach any improved method as such for iodine delivery or cost-effective iodization.
It will be evident from the prior art above that elemental iodine and iodide salts are preferred from the viewpoint of bioavailability but no attempt has been made so far in the literature to supply elemental iodine via the vehicle of salt. This would be a highly desirable objective especially if such elemental iodine can be delivered through salt in easy and cost-effective manner.
Reference may be made to Vogel's “Text Book of Quantitative Inorganic Analysis”, 4th Edition, 1978, pp 371, wherein the following chemical equations are reported for the reaction of elemental iodine with alkali.3I2+6OH→3I−+3IO−+3H2O  (eq 1)3IO−→2I−+IO3−  (eq 2)Net: 3I2+6OH→5I−+IO3−+3H2O  (eq 3)
Reference may be made to Encyclopedia of Chemical technology, 4th edition, Kirk & Othmer, 1992, Vol 19, pp 1084, wherein the iodizing agents normally used for salt iodization, namely KI and KIO3, are prepared from the product mixture of eq 3 which entails additional cost. Indeed, it is reported that market price of USP sodium iodide is 1.8-2.0 times the I2 price. Similar is the situation for potassium iodate.
Reference may once again be made to Vogel's “Text Book of Quantitative Inorganic Analysis”, 4th Edition, 1978, wherein it reported on pp 386 that iodide and iodate can be made to react in presence of 0.1-2.0 M HCl medium as per the reaction of eq. 4.IO3−+5I−+6H+→3I2+3H2O  (eq 4)
Reference may be made to U.S. Pat. No. 6,740,253 dated 25 May, 2004 by G. Ramachandraiah, P. K. Ghosh et al. wherein the use of bromide-bromate couple, that follows similar chemistry to eqs 1-4, has been reported as a latent source of bromine for preparation of bromine addition compounds.
Reference may be made to “A Handbook for Quality Control Personnel in Production and Monitoring of Iodised Salt” issued by Salt Commissioner, Government of India, Ministry of Industries, Jaipur, February 1994 wherein the methodology of eq 4 is utilized for estimation of iodine contents of salts that are iodized with iodate. In the method adopted, the salt is dissolved in water and excess quantity of KI is added along with acid. The liberated iodine is titrated with sodium thiosulphate of known concentration. No one has however considered the use of a mixture of iodide and iodate as iodizing agent to carry out similar chemistry in the body to release elemental iodine.
Reference may be made to any book of medical science wherein it is stated that whereas the pH in the mouth is typically 7.0-7.5, gastric juice in the stomach contains significant concentration of HCl and, consequently, a pH<3.0 that would be suitable for converting the latent elemental iodine into active elemental iodine for absorption by the body.